#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

struct TreeNode {
	int val;
	struct TreeNode* left;
	struct TreeNode* right;
};

struct TreeNode* invertTree(struct TreeNode* root) {
	if (root == NULL) return NULL;
	invertTree(root->left);
	invertTree(root->right);
	struct TreeNode* tmp = root->left;
	root->left = root->right;
	root->right = tmp;
	return root;
}